parallelogram law

Theorem 1

In an inner product space (http://planetmath.org/InnerProductSpace), let $x$ and $y$ be vectors. Then

$${\parallel x+y\parallel }^2+{\parallel x-y\parallel }^2=2{\parallel x\parallel }^2+2{\parallel y\parallel }^2.$$

Title	parallelogram law
Canonical name	ParallelogramLaw1
Date of creation	2013-03-22 16:08:02
Last modified on	2013-03-22 16:08:02
Owner	Mathprof (13753)
Last modified by	Mathprof (13753)
Numerical id	9
Author	Mathprof (13753)
Entry type	Theorem
Classification	msc 46C05
Related topic	ParallelogramLaw
Related topic	GeneralizationOfTheParallelogramLaw